Hypo eliminator solution



"Patented Jan. 4,1944

HYPO ELIMINATOR SOLUTION Lowell E. Mnehler, Rochester, N. Y.,-assignor to Eastman Kodak Company,

corporation of New Jersey No Drawing.

Application September 30, 1941, Serial No. 413,001

6 Claims. (01. 95-88) V This invention relates to solutions for use in the elimination of hypo from photographic images.

In the processing of photographic developingout materials such as gelatino-silver halide emulsions coated on paper, film, or glasssupports, if after fixation, the hypo (sodium or ammonium thiosulfate) is not completely eliminated from the processed material by washing or other means, under suitable conditions of temperature and humidity during storage, the silver image will tend to fade. This change involves conversion or some of the silver to less visible yellowish silver sulfide.

When one uses alkaline aqueous solutions containing compounds which form complex silver compounds, such as solutions of ammonia or amines, for the purpose of treating fixed paper prints, films, and plates to assist in the removal of the thiosulfate compounds during the treatment or in subsequent washing, or to act in conjunction with hydrogen peroxide in suitable concentrations for' sufliciently oxidizing the thiosulfate to neutral sulfate, it is found that the tone of the images, particularly those of finegrain materials such as prints, is altered from a warm black to a more bluish-black in the low and intermediate densities and to a warmer or less dense black in the higher densities. This eflect while desirable for certain purposes is, by virtue of the alteration in tone, sometimes undesirable.

It has been found that this alteration of tone can be decreased, and in some cases prevented by adding to the ammonia or amine-containing solution a soluble compound which is capable of forming silver compounds which are insoluble or slightly or difiicultly soluble in the ammonia or amine solution. Suitable compounds in all such solutions including those containing hydrogen peroxide, are alkali metal halides, such as potassium bromide and potassium iodide. The halide acids, hydrobromic and hydriodic, and their soluble ionizable salts with ammonia, organic amines, and other organic compounds may also be employed in place of the alkali metal bromides and iodides. In addition, organic reactants for silver are also eiiective.

The method used for treating prints in the manner of my invention includes: washing the fixed prints for about 10 to minutes, treating with the alkaline peroxide solutions for 5 to 10 minutes, and washing for 5 to 10 minutes. In

case alkaline solutions containing no peroxide are used, the prints may either be washed or not washed prior to treatment, as desired. Treatment may be from 2 to 10 minutes followed by sufiicient washing, for example, about 30 minutes. The degree of elimination or hypo depends both upon the time of treatment and the degree of washing.

The following examples show typical solutions which may be used according to my invention,

however, these examples are intended to be 11- lustrative only, and are not exhaustive of the variationsand equivalents contemplated by my invention.

I Example 1 Water cc 500 Hydrogen peroxide (3% solution).. cc -500 Ammonia 10 Potassium bromide. grams.. 1- 10 Water to make liter 1 The amount of bromide in the above formula is not critical, however, the indicated range gives satisfactory results. In caseit is desired to use potassium iodide in place of bromide, about 0.1 to about 2.0 grams is satisfactory.

The following organic reactants for silver may be substituted for bromide or iodide'in the above example:

, Gram 1,2,3-benzoi2riazole 0.1-1.0 23- (or 6-) bromobenzotriazole 0.1-1.0 S-nitrobenzimidazole 0.1-0.5 5- (or 7-) nitroindazole 0.1-0.5 5-aminotetrazole 0.1-1.0 2-aminobenzothiazole 0.1-1.0 2-acetylaminobenzothiazole 0.1-0.5

The organic compounds may be added as alcohol solutionsor in the form of their water oluble salts. When sufliciently soluble in water such as with benzotriazole, they may be added directly.

Example 2 Water liter 1 Ammonia (28 per cent) cc 5-25 To this solution may be added any one of the following:

Example 3 The solid chemicals either mixed or unmixed and packaged for later dissolving in a liter of water to make an ammoniacal hypo eliminator bath, may contain to 30 grams of 2-amino-2- methyl-1,3-pr0pandiol and one of the addition substances shown in Example 2, such as 1 to grams of potassium bromide.

The 2-amino-2-methyl-1,3-propandiol compound may be replaced by a similar quantity of a polyalkylene polyamine such as piperazine, diiso-propanolamine, or other solid water soluble alkaline reacting amine or substituted amine the normal solutions of which give a pH value in the range 9.5--l2.0.

As another alternative for the solid amine, a

water soluble amine salt packaged to be used in conjunction with an inorganic alkali but not necessarily mixed with it may be employed to form a solution. In this manner amines which are not solid at ordinary temperatures may be generated in solution by the addition of alkalies such as sodium carbonate, trisodium phosphate, sodium hydroxide, lithium hydroxide, etc. Ammonium salts such as the chloride and sulfate may also be used in the same manner as the amine salts in conjunction with the inorganic alkalies.

Example 4 Grams Diethylamine hydrochloride 11 Trisodium phosphate (cryst.) 38

These solid chemicals may be placed in separate compartments of a 2-compartment package. Either compartment may contain 1.0 gram of potassium iodide. The chemicals of the two compartments are for the preparation of one liter of hypo eliminator solution.

Example 5 A concentrated solution for marketing to be diluted with water for use in preparing one liter of hypo eliminator solution may contain:

Grams Ethanolamine 10-20 Hydrobromic acid 1- 5 or Hydriodic acid 0.2-1.5

The term ammoniaca as used herein is not intended to limit the scope of my inventionto or the silver images. Thus, sodium chloride is not suitable for use in the solutions of my invention since silver chloride is readily soluble in ammonia. In the ammoniacal peroxide solutions of my invention the compounds appear to precipitate the silver of silver-thiosulfate complexesand delay or prevent both its reduction to silver and the formation of silver sulfide on the image grains. The addition compounds are likewise effective in alkaline and alkaline peroxide hypo eliminator solutions containing no ammonia or amine.

It is to be understood that the disclosure herein is by way of example and that I consider as included in my invention all modifications and equivalents falling within the scope of the appended claims.

What I claim is:

1. The method of elimination of hypo from photographic silver images which comprises treating said images with an ammoniacal peroxide solution of a soluble ionizable halide selected from the group consisting of hydrobromic acid and hydriodic acid and their water soluble ionizable salts with a basic material selected from the class consisting of organic amines, ammonia, and the alkali metal elements.

2. The method of elimination of hypo from photographic silver images which comprises treating said images with an ammoniacal peroxide solution of potassium bromide.

3. The solid chemicals packaged for We in making an ammoniacal peroxide hypo eliminator bath by dissolving in water for use in the elimination of hypo from photographic silver images, comprising 2 amino 2 methyl-1,3-propandiol and a soluble ionizable halide selected from the group consisting of hydrobromic acid and hydriodic acid and their soluble ionizable salts with a basic material selected from the class consisting of organic'amines, ammonia and the alkali metal elements.

4. The method of eliminating hypo from photographic silver images, which comprises treating said images with an ammoniacal peroxide solution of a compound selected from the group consisting of alkali metal bromide and iodide.

5. The method of eliminating hypo from photographic silver images, which comprises treating said images with an ammoniacal peroxide solution of potassium iodide.

6. The solid chemicals packaged for use in the making of an ammoniacal peroxide hypo eliminator bath by dissolving in water for use in the elimination of hypo from photographic silver images, comprising a solid alkaline reacting water soluble amine and a soluble ionizable halide selected from the group consisting of hydrobromic acid and hydriodic acid and their soluble ionizable salts with a basic material selected from the class consisting of organic amines, ammonia and the alkali metal elements.

' LOWELL E. MUEHLER. 

